This invention relates generally to wavelength division multiplexed and/or high bandwidth optical communications systems, and more particularly to the compensation for chromatic dispersion in such systems.
With the advent of substantial new uses for electro/optic systems, there exists a greater need to efficiently switch Wavelength Division Multiplexed (WDM), and Dense Wavelength Division Multiplexed (DWDM), and/or high bandwidth signals on optical fibers.
U.S. patent Ser. No, 5,771,320 discloses a free space optical switching and routing system utilizing a switchable grating based approach together with novel noise suppression techniques. This family of devices provides for an optical switching and routing system that is useful for interconnecting any of an input array""s optical channels to any of an output array""s optical channels.
In systems such as the one described in U.S. patent Ser. No, 5,771,320, the beam paths, other than the un-deviated path, experience varying amounts of travel in an angularly dispersed condition. The longer the travel in the angularly dispersed condition, the larger the lateral displacements that accumulate between differing spectral components. This length of travel in the angularly dispersed condition increases as separation of the deviated path from the un-deviated path increases.
There is a need for methods and systems that compensate for the lateral chromatic dispersion and lateral shifts induced by the switching/routing optical system.
It is therefore an object of this invention to provide methods and systems that compensate for the lateral chromatic dispersion and the lateral shifts induced by the propagation of beams through the switching/routing optical system.
It is a further object of this invention to provide systems that that compensate for the lateral chromatic dispersion and lateral shifts induced by the propagation of beams through the switching/routing optical system which can be easily integrated into present switching/routing systems.
It is a still further object of this invention to provide a mirror array system for the deflection of beams in achromatized switching/routing optical systems and method of fabricating same.
The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention described hereinbelow.
The present invention provides methods and systems that compensate for the lateral chromatic dispersion and lateral shifts induced by the propagation of beams through a switching/routing optical system.
In general, the output beams of switching/routing optical systems may be angularly and/or laterally dispersed. This invention relates to the compensation of lateral chromatic dispersion. The lateral chromatic dispersion in the beams can cause Wavelength Dependent Loss (WDL) in coupling to optical fibers or other transmission or detection devices.
Utilizing the method of the present invention, an output of an switching/routing optical system that produces lateral chromatic dispersion in the output beams is achromatized by adding an equal amount of lateral chromatic dispersion in the opposite direction for all outputs. This is accomplished by, first, deviating the output optical beam to a direction in an angular sense opposite to the angular sense of the dispersing portion of the switching/routing optical system; and, then, propagating the output optical beam a distance sufficient to substantially compensate the lateral chromatic dispersion induced by the switching/routing optical system; and, finally, deviating the output optical beam to an angular direction optically parallel to the original input beams of the switching/routing optical system.
A system of this invention includes a switching/routing sub-system, and a lateral chromatic corrector comprising a deviating optical sub-system and a re-deviating optical sub-system. The deviating optical sub-system is capable of deviating the output optical beam to a predetermined angular direction. In one embodiment, the predetermined angular sense of this deviation is opposite to the angular sense of the initial deviation produced by the switching/routing optical system. The re-deviating optical sub-system is capable of receiving the deviated output optical beam and re-deviating the deviated output optical beam to another predetermined angular direction that is optically parallel to the original angular direction of the input beam. The path length of the deviated output optical beam is sufficiently long to substantially compensate the lateral chromatic dispersion induced by the switching/routing optical system. In one embodiment, the deviating optical sub-system includes a deviating diffraction grating; and, the re-deviating optical sub-system includes a re-deviating diffraction grating. The gratings can be volume holographic diffraction gratings similar to those used in one embodiment of the switching/routing optical system.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims.